What to Do When You First Suspect Infidelity
Start keeping a careful log of your wife’s behavior immediately. Raoul Felder, a New York divorce attorney who represented Rudy Giuliani, advises keeping one record of her actions (“She came in late at night”) and one of her expenses (“She took $100 from my wallet”). The money side could ultimately prove how much she spent on the affair, which can usually be subtracted from a settlement.

When to Confront Her
Don’t accuse your wife of having an affair until you’ve been keeping a log for at least a month. If you want to save your marriage, Dr. Luann Linquist, author of Secret Lovers: Affairs Happen . . . How to Cope, suggests saying, “I want to make sure you’re happy. What could I do to make things better?” Maybe your wife just wants you to be at home more. But if she brings up something you can’t change, like how boring she thinks you are, prepare to submit the log.

When to File the Papers
You want to serve papers when you have the lowest financial profile possible. If you’re expecting a big bonus, file before the cash lands in your account. “Otherwise it’s going to be sitting there with a big sign on it that says take me,” says Brett Kimmel, a New York lawyer who handled Beastie Boy Adam Horovitz’s divorce from Ione Skye. And don’t start the process until you’ve begun keeping the log. “Toward the end of a marriage, people tend to go on a spending spree,” Kimmel says. When the right time does come and you pull the trigger, the first thing she’s going to ask for is temporary financial support to pay the household bills. When she says this comes to about $30,000, you can use your notebook to prove that the actual cost is half that.

What to Tell the Boss
Your boss needs a heads-up about why your work might suffer for a couple of months, but he doesn’t need a play-by-play of the breakdown of your marriage. Be brief. Explain that things are rocky at home and apologize for any sloppiness on your part. When well-meaning colleagues ask about the wife you’ve stopped mentioning, don’t broadcast her infidelity. It just makes you look bad. Peter Post, a director of the Emily Post Institute and the author of Essential Manners for Men, suggests saying, “You may not be aware, but we’re having some problems right now and we’re working on it. Thanks for asking.”

What to Tell Your Friends
Resist the urge to trash her. Instead, shore up sympathy and play the Nick Lachey card—say you wish you could have made her happier. “Tell your friends, ‘I feel hurt. I feel betrayed,’” says Marcella Weiner, coauthor of Cheaters. “‘There was nothing I wouldn’t do for her. I don’t know where I went wrong.’” Just make sure no one finds your notebook.